/**
 * ***************************************************************************** Copyright (c)
 * 2012-2015 Red Hat, Inc. All rights reserved. This program and the accompanying materials are made
 * available under the terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 *
 * <p>Contributors: Red Hat, Inc. - initial API and implementation
 * *****************************************************************************
 */
package org.eclipse.che.ide.ext.java.jdt.text;

import java.util.ArrayList;
import java.util.List;
import org.eclipse.che.ide.api.editor.text.BadLocationException;
import org.eclipse.che.ide.api.editor.text.Region;
import org.eclipse.che.ide.api.editor.text.RegionImpl;
import org.eclipse.che.ide.ext.java.jdt.text.AbstractLineTracker.DelimiterInfo;

/**
 * Abstract, read-only implementation of <code>ILineTracker</code>. It lets the definition of line
 * delimiters to subclasses. Assuming that '\n' is the only line delimiter, this abstract
 * implementation defines the following line scheme:
 *
 * <ul>
 *   <li>"" -> [0,0]
 *   <li>"a" -> [0,1]
 *   <li>"\n" -> [0,1], [1,0]
 *   <li>"a\n" -> [0,2], [2,0]
 *   <li>"a\nb" -> [0,2], [2,1]
 *   <li>"a\nbc\n" -> [0,2], [2,3], [5,0]
 * </ul>
 *
 * This class must be subclassed.
 */
abstract class ListLineTracker implements LineTracker {

  /** The line information */
  private final List<Line> fLines = new ArrayList<Line>();

  /** The length of the tracked text */
  private int fTextLength;

  /** Creates a new line tracker. */
  protected ListLineTracker() {}

  /**
   * Binary search for the line at a given offset.
   *
   * @param offset the offset whose line should be found
   * @return the line of the offset
   */
  private int findLine(int offset) {

    if (fLines.size() == 0) return -1;

    int left = 0;
    int right = fLines.size() - 1;
    int mid = 0;
    Line line = null;

    while (left < right) {

      mid = (left + right) / 2;

      line = (Line) fLines.get(mid);
      if (offset < line.offset) {
        if (left == mid) right = left;
        else right = mid - 1;
      } else if (offset > line.offset) {
        if (right == mid) left = right;
        else left = mid + 1;
      } else if (offset == line.offset) {
        left = right = mid;
      }
    }

    line = (Line) fLines.get(left);
    if (line.offset > offset) --left;
    return left;
  }

  /**
   * Returns the number of lines covered by the specified text range.
   *
   * @param startLine the line where the text range starts
   * @param offset the start offset of the text range
   * @param length the length of the text range
   * @return the number of lines covered by this text range
   * @throws BadLocationException if range is undefined in this tracker
   */
  private int getNumberOfLines(int startLine, int offset, int length) throws BadLocationException {

    if (length == 0) return 1;

    int target = offset + length;

    Line l = (Line) fLines.get(startLine);

    if (l.delimiter == null) return 1;

    if (l.offset + l.length > target) return 1;

    if (l.offset + l.length == target) return 2;

    return getLineNumberOfOffset(target) - startLine + 1;
  }

  /* @see org.eclipse.jface.text.ILineTracker#getLineLength(int) */
  public final int getLineLength(int line) throws BadLocationException {
    int lines = fLines.size();

    if (line < 0 || line > lines) throw new BadLocationException();

    if (lines == 0 || lines == line) return 0;

    Line l = (Line) fLines.get(line);
    return l.length;
  }

  /* @see org.eclipse.jface.text.ILineTracker#getLineNumberOfOffset(int) */
  public final int getLineNumberOfOffset(int position) throws BadLocationException {
    if (position < 0 || position > fTextLength) throw new BadLocationException();

    if (position == fTextLength) {

      int lastLine = fLines.size() - 1;
      if (lastLine < 0) return 0;

      Line l = (Line) fLines.get(lastLine);
      return (l.delimiter != null ? lastLine + 1 : lastLine);
    }

    return findLine(position);
  }

  /* @see org.eclipse.jface.text.ILineTracker#getLineInformationOfOffset(int) */
  public final Region getLineInformationOfOffset(int position) throws BadLocationException {
    if (position > fTextLength) throw new BadLocationException();

    if (position == fTextLength) {
      int size = fLines.size();
      if (size == 0) return new RegionImpl(0, 0);
      Line l = (Line) fLines.get(size - 1);
      return (l.delimiter != null
          ? new Line(fTextLength, 0)
          : new Line(fTextLength - l.length, l.length));
    }

    return getLineInformation(findLine(position));
  }

  /* @see org.eclipse.jface.text.ILineTracker#getLineInformation(int) */
  public final Region getLineInformation(int line) throws BadLocationException {
    int lines = fLines.size();

    if (line < 0 || line > lines) throw new BadLocationException();

    if (lines == 0) return new Line(0, 0);

    if (line == lines) {
      Line l = (Line) fLines.get(line - 1);
      return new Line(l.offset + l.length, 0);
    }

    Line l = (Line) fLines.get(line);
    return (l.delimiter != null ? new Line(l.offset, l.length - l.delimiter.length()) : l);
  }

  /* @see org.eclipse.jface.text.ILineTracker#getLineOffset(int) */
  public final int getLineOffset(int line) throws BadLocationException {
    int lines = fLines.size();

    if (line < 0 || line > lines) throw new BadLocationException();

    if (lines == 0) return 0;

    if (line == lines) {
      Line l = (Line) fLines.get(line - 1);
      if (l.delimiter != null) return l.offset + l.length;
      throw new BadLocationException();
    }

    Line l = (Line) fLines.get(line);
    return l.offset;
  }

  /* @see org.eclipse.jface.text.ILineTracker#getNumberOfLines() */
  public final int getNumberOfLines() {
    int lines = fLines.size();

    if (lines == 0) return 1;

    Line l = (Line) fLines.get(lines - 1);
    return (l.delimiter != null ? lines + 1 : lines);
  }

  /* @see org.eclipse.jface.text.ILineTracker#getNumberOfLines(int, int) */
  public final int getNumberOfLines(int position, int length) throws BadLocationException {

    if (position < 0 || position + length > fTextLength) throw new BadLocationException();

    if (length == 0) // optimization
    return 1;

    return getNumberOfLines(getLineNumberOfOffset(position), position, length);
  }

  /*
   * @see org.eclipse.jface.text.ILineTracker#computeNumberOfLines(java.lang.String)
   */
  public final int computeNumberOfLines(String text) {
    int count = 0;
    int start = 0;
    DelimiterInfo delimiterInfo = nextDelimiterInfo(text, start);
    while (delimiterInfo != null && delimiterInfo.delimiterIndex > -1) {
      ++count;
      start = delimiterInfo.delimiterIndex + delimiterInfo.delimiterLength;
      delimiterInfo = nextDelimiterInfo(text, start);
    }
    return count;
  }

  /* @see org.eclipse.jface.text.ILineTracker#getLineDelimiter(int) */
  public final String getLineDelimiter(int line) throws BadLocationException {
    int lines = fLines.size();

    if (line < 0 || line > lines) throw new BadLocationException();

    if (lines == 0) return null;

    if (line == lines) return null;

    Line l = (Line) fLines.get(line);
    return l.delimiter;
  }

  /**
   * Returns the information about the first delimiter found in the given text starting at the given
   * offset.
   *
   * @param text the text to be searched
   * @param offset the offset in the given text
   * @return the information of the first found delimiter or <code>null</code>
   */
  protected abstract DelimiterInfo nextDelimiterInfo(String text, int offset);

  /**
   * Creates the line structure for the given text. Newly created lines are inserted into the line
   * structure starting at the given position. Returns the number of newly created lines.
   *
   * @param text the text for which to create a line structure
   * @param insertPosition the position at which the newly created lines are inserted into the
   *     tracker's line structure
   * @param offset the offset of all newly created lines
   * @return the number of newly created lines
   */
  private int createLines(String text, int insertPosition, int offset) {

    int count = 0;
    int start = 0;
    DelimiterInfo delimiterInfo = nextDelimiterInfo(text, 0);

    while (delimiterInfo != null && delimiterInfo.delimiterIndex > -1) {

      int index = delimiterInfo.delimiterIndex + (delimiterInfo.delimiterLength - 1);

      if (insertPosition + count >= fLines.size())
        fLines.add(new Line(offset + start, offset + index, delimiterInfo.delimiter));
      else
        fLines.add(
            insertPosition + count,
            new Line(offset + start, offset + index, delimiterInfo.delimiter));

      ++count;
      start = index + 1;
      delimiterInfo = nextDelimiterInfo(text, start);
    }

    if (start < text.length()) {
      if (insertPosition + count < fLines.size()) {
        // there is a line below the current
        Line l = (Line) fLines.get(insertPosition + count);
        int delta = text.length() - start;
        l.offset -= delta;
        l.length += delta;
      } else {
        fLines.add(new Line(offset + start, offset + text.length() - 1, null));
        ++count;
      }
    }

    return count;
  }

  /*
   * @see org.eclipse.jface.text.ILineTracker#replace(int, int, java.lang.String)
   */
  public final void replace(int position, int length, String text) throws BadLocationException {
    throw new UnsupportedOperationException();
  }

  /* @see org.eclipse.jface.text.ILineTracker#set(java.lang.String) */
  public final void set(String text) {
    fLines.clear();
    if (text != null) {
      fTextLength = text.length();
      createLines(text, 0, 0);
    }
  }

  /**
   * Returns the internal data structure, a {@link List} of {@link Line}s. Used only by {@link
   * TreeLineTracker#TreeLineTracker(ListLineTracker)}.
   *
   * @return the internal list of lines.
   */
  final List<Line> getLines() {
    return fLines;
  }
}
